Oscillating-current generator



L. -DE FOREST. OSCILLATING CURRi-INT GENERATOR.

APPLICATION FILED JUNE 16, I916- 1,329,758. Patented Feb. 3,1920.

315 alto age B UNITED STATES PATENT OFFICE.

LEE DE FOREST, OF NEW YORK, N. Y., ASSIGNOR TO DE FOREST RADIO TELEPHONE AND TELEGRAPH COMPANY, OF NEW YORK, N. Y., A CORPORATION OF DELAWARE;

OSCILLATIN G-CURREN T GENERATOR;

Specification of Letters Patent. Patented Feb. 3, 19205 Original application filed March 26, 1915, Serial No. 17,225. Patent No. 1,221,034. Divided and this appli cationfiled June 16, 1916. Serial No. 104,074.

To all whom it may concern:

Be it known that I, LEE on Fonns'r, a citizen of the United States, and residing at New York, county of Bronx, State of New York, have made a certain new and useful Invention in Oscillating Current Generators,of which the following is a specification.

This invention relates to oscillating current generators and is subject matter divided from my copending application, which has since issued on April 3d, 1917, as Letters Patent No. 1,221,034.

The object of the invention is to provide a high frequency oscillating current generator which is simple and efiicient.

Other objects of the invention will appear more fully hereinafter.

The invention consists substantially in the construction, combination, location and relative arrangement of parts all as will be more fully hereinafter set forth, as shown in the accompanying drawings, and finally pointed out in the appended claim.

Figure 1 is a circuit diagram showing one arrangement embodying my invention.

Figs. 2 and 3 are modified constructions of oscillation generators embodying my invention.

Fig. 4 is a sectional view taken on the line 4, 4, Fig. 1, and looking in the direction of the arrows.

Referring to the drawings,-

1 designates generally an evacuated vessel which is provided with two chambers 2 and 3 Which are united by a narrow passage 4. In these two chambers I place electrodes, which may be of any desirable material, but for illustrative purposes, I have shown the same to be of mercury or an amalgam thereof at 5, (3. A source of electromotive force, indicated at 7, supplies a current through a variable resistance 8 to the electrodes 5, 6, to heat the same and cause a vapor are column to form in the passage 4.

In a chamber 3*, forming part of the evacuated vessel 1 and communicating with the mercury arc passage 4, are located two cold electrodes 9 and 10, preferably arranged at different distances from the vapor arc column maintained in the passage 4.

The electrode 9 is electrically connected to oneterminal of a source of electromotive force 11. I have found it preferable to employ a direct current generator, as shown,

but my invention is not to be limited thereto. One terminal of the current source 11 is connected to an electrode 9, and the other terminal of said current source 11 is connected to one of the cathode electrodes of the evacuated vessel, as, for instance, the electrode 5. The circuit connection between electrode 9 and source 11, preferably contains an inertia coil indicated at 12.

It is of advantage to maintain the electrodes 9 and 10, cool, and this may be accomplished in any suitable convenient manner. In the case of electrode 9 I have shown a simple arrangement wherein I employ a reservoir 13 which; is provided with pipes 14 opening upon the electrode 9 and adapted to allow a cooling medium such as air, water, oil, or the like, to circulate therethrough.

The electrode 10 maybe of any desired shape, or material, but I have found it advantageous to employ therefor abent holtherethroiigh. The cooling medium may be supplied from reservoir 13, and for the sake of avoiding confusion in the drawing the connections between the electrode 10 and reservoir 18 have been omitted. My invention, however, is not to be limited or restricted in this respect.

In theusual and well known way, I associate an oscillating circuit with the two cold electrodes 9 and 10. This circuit consists of the usual condenser 15, and inductance l6, arran ed in series with electrodesQ and 10 and with each'other. Ifdesired, and-as shown, a switch or other form of circuit make and break device 17 may also be placed in series in this oscillating circuit. If desired, and as shown, a variable capacity, such as a condenser 18, may be shunted around the inductance 16, but my invention in its broad scope is not to be limited or restricted to this detail.

I propose to connect a high resistance 19 to the electrode 10 and the vapor arc column maintained in the passage 4, to form a high resistance leak path between said electrodes. The purpose of this leak path 7 is to conduct oil the excessive charge which may accumulate on the electrode and thereby reduce the eflicient operation of the creased in intensity provided the period of the second oscillating circuit is madeequal to that of the first oscillating circuit. It is not essential, however, to employ this second oscillating circuit, and my invention, therefore, as defined by the claim, is not to be limited or restricted in this respect; therefore, the elements 20, 21 may be omitted if desired. When the two oscillating circuits are employed, however, the inductance elements 16, 20, thereof, should be inducner for radio operation.

tively associated,as shown.

A load or output circuit may be associated, either inductively or conductively .with ,one or both of the above described oscillating circuits. In the arrangement shown, the load circuit is made up of a variable inductance 22 connected intermediate the radiating antenna 23 and the ground or earth24 in the usual and well known man- T he natural period of the load circuit should be equal to that of the first or original oscillating circuit.

In Fig. 2 I show a modified form of evacuated vessel oscillator, wherein the heated electrode may be a filament instead of a vapor arc above described. In this form of my invention the cold electrode 10 is shown in section as a metal tube inserted in the constricted portion of the chamber 3 of the vessel 1, immediately above the passage 4. Instead of employing a column of vapor, in desired, and as shown, a heavyfilament oftungsten, or platinum coated with oxid of calcium or other suitable material may be employed as indicated at 25. In this instance, heavy leading in wires 26 are employed to support the heating filament 25. The circuit connections and the operation of this modification of my invention is similar to the above described arrangement shown in Fig. 1.

If desired, instead of employing the beercury or other form of electrodes 6, 5 in chambers 2, 3 of Fig. 1, or the filament, arrangement'of Fig. 2, one of the chambers 2, 3, may be supplied with a mercury. or other form of electrode such as 5 or 6, while the other associated chamber may be provided with a suitable non-vaporizable electrode such as indicated at 27, Fig. 3.

The exact operation involved in a generator having the construction shown in the drawings; and. asabove described I have not as yet been able to fully and completely understand. I have discovered however that such an arrangement or arrangements do operate as a generator of high frequency 0'scillations suitable for radio work, and, whether correct or not the oscillatory phe; nomena involved'in the operation of the apparatus may be described in a general way as follows:

If the generator 11 is a direct current source a negative current is set up across the oscillator by means of the thermions passing from the hot electrode 25, 27, or the vapor arc in passage 4 as the case may be, to the cold electrode 9. A negative chargi impressed upon the cold electrode 10 wi greatly reduce the flow of thermions from the hot electrode or vapor arc to the electrode 9, or, in other words, will increase the potential drop between the cold electrode 9 and the hot electrode. Therefore, if the electrical connection between the electrode 10 and the electrode 9 be suddenly estab- V lished by closing the switch or circuit maker 17, the positive potential of the electrode 9 and of the-positive terminal of condenser 18 will be suddenly increased. Further, any positive charge on the electrode 10 will be rapidly carried away by action of the negatively charged thermions from the hot electrode attracted thereto, inasmuch as the capacity of the stopping condenser 15 is small. Thus a difi'erence in potential is quickly established between the two terminals of condenser 18. The inductance coil 16 prevents this diiierence. of potential across the condenser 18 from immediately equalizing and in consequence an oscillatory discharge is set up through the inductance 16. At the end of a half period of this discharge the potential of one armature of the condenser 18 is therefore reduced or made negative, while that on the other side of the condenser is made positive relative thereto. The reduction of the positive potential at one terminal of condenser 18, and on the elec trode 9 causes a sudden increase of positive current from source 11 which again charges one terminal of condenser 18 positively, and a negative current again sets up across coil 16 to the other terminal of said condenser and to the electrode 10. This inrush of negative charge to the electrode 10 will again reduce the passage of thermions from the hot electrode to the cold electrode 9, that is, will again still further increasethe positive potential. of 9 and the corresponding terminal of condenser 18 relative to the other terminal of said condenser. Thus condenser 18 will once more begin to discharge a positive cuits and in the oscillator are equal to any and a plate electrode located within said further increase in the energy representing vessel, and a hollow grid shaped electrode the oscillations. also located within said vessel and interposed Having now described the objects and nabetween said hot and plate electrodes, to per- 5 ture of my invention, and various arrangemit a cooling fluid to be passed through said 15 ments for accomplishing the same, what I grid electrode from the exterior of said claim as new and useful and desire to secure vessel. by Patents, is,-- r In testimony whereof I have hereunto set In an audion structure, the combination m hand on this 5th day of June, A. D., 1916. 10 with an evacuated vessel, of a hot electrode LEE 1m FOREST. 

